mpMRI of the Prostate (MR-Prostatography): Updated Recommendations of the DRG and BDR on Patient Preparation and Scanning Protocol. / mpMRT der Prostata (MR-Prostatografie): Aktualisierte Empfehlungen der DRG und des BDR zur Vorbereitung und Durchführung.

The Working Group Uroradiology and Urogenital Diagnosis of the German Roentgen Society (DRG) revised and updated the recommendations for preparation and scanning protocol of the multiparametric MRI of the Prostate in a consensus process and harmonized it with the managing board of German Roentgen Society and Professional Association of the German Radiologist (BDR e. V.). These detailed recommendation define the referenced "validated quality standards" of the German S3-Guideline Prostate Cancer and describe in detail the topic 1. anamnestic datas, 2. termination of examinations and preparation of examinations, 3. examination protocol and 4. MRI-(in-bore)-biopsy. KEY POINTS:: · The recommendations for preparation and scanning protocol of the multiparametric MRI of the Prostate were revised and updated in a consensus process and harmonized with the managing board of German Roentgen Society (DRG) and Professional Asssociation of the German Radiologist (BDR).. · Detailed recommendations are given for topic 1. anamnestic datas, 2. termination and preparation of examinations, 3. examination protocoll and 4. MRI-(in-bore)-biopsy.. · These recommendations define the referenced "validated quality standards" of the German S3-Guideline Prostate Cancer.. CITATION FORMAT: · Franiel T, Asbach P, Beyersdorff D et al. mpMRI of the Prostate (MR-Prostatography): Updated Recommendations of the DRG and BDR on Patient Preparation and Examination Protocol. Fortschr Röntgenstr 2021; 193: 763 - 776.

Histopathological to multiparametric MRI spatial mapping of extended systematic sextant and MR/TRUS-fusion-targeted biopsy of the prostate.

PURPOSE: MRI has limited ability to detect multifocal disease or the full extent of prostate involvement with clinically significant prostate cancer (sPC). We compare the spatial co-localization at sextant resolution of MRI lesions and histopathological mapping by combined targeted and extended systematic biopsies. MATERIALS AND METHODS: Sextants were mapped for sPC (ISUP group ≥ 2) by 24-core transperineal systematic biopsies in 316 patients with suspicion for sPC and by MR lesions of PI-RADS score of ≥ 3. The gold standard is combined systematic (median 23 cores) and targeted biopsies. RESULTS: Of 316 men, 121 (38%) harbored sPC. Of these 121 patients, 4 (3%) had a negative MRI. MRI correctly identified 117/121 (97%) patients with sPC. In these patients, mpMRI missed no additional sPC in 96 (82%), while MRI-negative sPC lesions were present in 21 patients (18%). Of 1896 sextants, 379 (20%) harbored sPC. MR-positive sextants contained sPC in 26% (337/1275), compared to 7% (42/621) in MR-negative sextants. On a patient basis, sensitivity was 0.97, specificity 0.22, positive predictive value 0.43, and negative predictive value 0.91. On a sextant basis, sensitivity was 0.73, specificity 0.38, positive predictive value 0.26, and negative predictive value 0.93. CONCLUSION: MpMRI mapping agreed well with histopathology with, at the observed sPC prevalence and on a patient basis, excellent sensitivity and negative predictive value, and acceptable specificity and positive predictive value for sPC. However, 18% of sPC was outside the mpMRI mapped region, quantifying limitations of MRI for complete localization of disease extent. KEY POINTS: • Currently, exclusive MRI mapping of the prostate for focal treatment planning cannot be recommended, as significant prostate cancer may remain untreated in a substantial number of cases. • At the observed sPC prevalence and on a patient basis, mpMRI has excellent sensitivity and NPV, and acceptable specificity and PPV for detection of prostate cancer, supporting its use to detect suspicious lesions before biopsy. • Despite the excellent global performance, 18% of sPC was outside the mpMRI mapped region even when a security margin of 10 mm was considered, indicating that prostate MRI has limited ability to completely map all cancer foci within the prostate.

Diffusion-weighted MRI treatment monitoring of primary hypofractionated proton and carbon ion prostate cancer irradiation using raster scan technique.

PURPOSE: To investigate parametric changes in the apparent diffusion coefficient (ADC) at multiple timepoints during and after completion of primary proton and carbon ion irradiation of prostate cancer (PCa) as compared with normal-appearing prostate parenchyma. MATERIALS AND METHODS: In all, 92 patients with histologically confirmed PCa received either proton or carbon ion hypofractionated radiotherapy (RT). All were prospectively evaluated with diffusion-weighted magnetic resonance imaging (DWI-MRI) at five timepoints: baseline, day 10 during therapy and 6 weeks, 6 months, and 18 months after treatment. Linear mixed models (LMM) were used to evaluate the effects of radiation, antihormonal therapy, time, and type of particle irradiation on manual ADC measurements. ADC differences related to prostate-specific antigen (PSA) relapse according to PSA thresholds and to Vancouver rules and Phoenix criteria were examined using LMM and unpaired Student's t-test. RESULTS: A measurable and continuous increase of tumor ADC measurements from baseline (1.194 × 10-3 mm2 /s) during (1.350 × 10-3 mm2 /s, day 10, P = 0.006) and after treatment (1.355/1.430/1.490 × 10-3 mm2 /s, week 6 / month 6 / month 18, P = 0.001/<0.001/<0.001) was found. ADC values of normal-appearing control tissue remained unchanged. Androgen deprivation (P ≥ 0.320), different PSA thresholds (P = 0.634), and PSA relapse criteria according to Vancouver rules (P ≥ 0.776) had no effect. A weak association between 18-month measurements and Phoenix criteria (P = 0.046) was found. CONCLUSION: ADC parametric changes were distinct in tumor tissue, highlighting the ability of diffusion MRI to evaluate different aspects of the microscopic pathophysiology. Although promising, their use as noninvasive imaging biomarkers requires further validation. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:850-860.

Mask-Adapted Background Field Removal for Artifact Reduction in Quantitative Susceptibility Mapping of the Prostate.

We propose an alternative processing method for quantitative susceptibility mapping of the prostate that reduces artifacts and enables better visibility and quantification of calcifications and other lesions. Three-dimensional gradient-echo magnetic resonance data were obtained from 26 patients at 3 T who previously received a planning computed tomography of the prostate. Phase images were unwrapped using Laplacian-based phase unwrapping. The background field was removed with the V-SHARP method using tissue masks for the entire abdomen (Method 1) and masks that excluded bone and the rectum (Method 2). Susceptibility maps were calculated with the iLSQR method. The quality of susceptibility maps was assessed by one radiologist and two physicists who rated the data for visibility of lesions and data quality on a scale from 1 (poor) to 4 (good). The readers rated susceptibility maps computed with Method 2 to be, on average, better for visibility of lesions with a score of 2.9 ± 1.1 and image quality with a score of 2.8 ± 0.8 compared with maps computed with Method 1 (2.4 ± 1.2/2.3 ± 1.0). Regarding strong artifacts, these could be removed using adapted masks, and the susceptibility values seemed less biased by the artifacts. Thus, using an adapted mask for background field removal when calculating susceptibility maps of the prostate from phase data reduces artifacts and improves visibility of lesions.

MRI of the Prostate: Recommendations on Patient Preparation and Scanning Protocol.

The Working Group Uroradiology and Urogenital Diagnosis of the German Roentgen Society has developed uniform recommendations for the preparation and implementation of prostate MRI. In the first part detailed recommendations are given in tabular form regarding 1. anamnestic data before prostate MRI, 2. termination of examinations and preparation of examinations, 3. examination protocol and 4. MRI-guided in-bore biopsy. In the second part, the recommendations are discussed in detail and relevant background information is provided. Key Points: · Uniform recommendations for prostate MRI has been developed from the Working Group Uroradiology and Urogenital Diagnosis of the German Roentgen Society.. · Necessary anamnestic data, recommendations for termination of examinations and prepararion of examinations, examination protocol and MRI guided in-bore biopsy are detailed expressed and documented.. Citation Format · Franiel T., Quentin M., Mueller-Lisse U. G. et al. MRI of the Prostate: Recommendations on Patient Preparation and Scanning Protocol. Fortschr Röntgenstr 2017; 189: 21 - 28.

Potential of quantitative susceptibility mapping for detection of prostatic calcifications.

PURPOSE: To evaluate whether quantitative susceptibility (QSM) may be used as an alternative to computed tomography (CT) to detect calcification in prostate cancer patients. MATERIALS AND METHODS: Susceptibility map calculation was performed using 3D gradient echo magnetic resonance imaging (MRI) data from 26 patients measured at 3T who previously received a planning CT of the prostate. Phase images were unwrapped using Laplacian-based phase unwrapping, the background field was removed with the V-SHARP method, and susceptibility maps were calculated with the iLSQR method. Two blinded readers were asked to identify peri- and intraprostatic calcifications. RESULTS: Average mean and minimum susceptibility values (referenced to iliopsoas muscle) of calcifications were -0.249 ± 0.179 ppm and -0.551 ± 0.323 ppm, and average mean and maximum intensities in CT images were 319 ± 164 HU and 679 ± 392 HU. Twenty-one and 17 out of 22 prostatic calcifications were identified using susceptibility maps and magnitude images, respectively, as well as more than half of periprostatic phleboliths depicted by CT. Calcifications in the prostate and its periphery were quantitatively differentiable from noncalcified prostate tissue in CT (mean values for calcifications / for noncalcified tissue: 71 to 649 / -1 to 83 HU) and in QSM (mean values for calcifications / for noncalcified tissue: -0.641 to 0.063 / -0.046 to 0.181 ppm). Moreover, there was a significant correlation between susceptibility values and CT image intensities for calcifications (P < 0.004). CONCLUSION: Prostatic calcifications could be well identified with QSM. Susceptibility maps can be easily obtained from clinical prostate MR protocols that include a 3D gradient echo sequence, rendering it a promising technique for detection and quantification of intraprostatic calcifications. LEVEL OF EVIDENCE: 1 J. Magn. Reson. Imaging 2017;45:889-898.

Dynamic contrast enhanced MRI monitoring of primary proton and carbon ion irradiation of prostate cancer using a novel hypofractionated raster scan technique.

PURPOSE: To characterize parametric changes measured by sequential dynamic contrast enhanced perfusion MRI (DCE-MRI) during primary proton and carbon ion irradiation of prostate cancer using a novel hypofractionated raster scan technique to determine the potential of pharmacokinetic analysis for monitoring treatment effects of this novel irradiation scheme. MATERIALS AND METHODS: Ninety-two patients were evaluated prospectively with DCE-MRI at baseline, day 10 during therapy, and 6weeks, 6months and 18months after treatment completion. After motion correction and co-registration to morphological T2-weighted images, tumors and normal appearing contralateral parenchyma (NACP) were segmented manually on T2W images and ROI statistics calculated for pharmacokinetic parameters K(trans), kep and ve using the standard Tofts model. RESULTS: The volume transfer constant (K(trans), p<0.001/p=0.010) and the leakage space partial volume (ve, p<0.001/p=0.005) showed a statistically significant increase during therapy with protons and carbon ions, respectively. Parametric increases occurred only in patients naive to antihormonal therapy (AHT), and were maximal 10days after the begining of treatment. The rate constant (kep) showed a significant increase only for proton, but not for carbon irradiation (p=0.021). Statistically significant differences between PC and NACP were observed for all parameters (p<0.001). AHT naïve patients with persistent PSA elevation above 1ng/ml at 12months experienced statistically significant elevation of K(trans) and ve compared to those with PSA suppression (p=0.04/p=0.023). CONCLUSION: DCE parametric changes following ion particle irradiation of the prostate have not been previously reported. Their development into potential non-invasive imaging biomarkers for assessment of treatment response and efficacy is expected to be aided by the data on the magnitude and temporal evolution of parametric responses of cancer and normal tissue during and after therapy presented here, especially the changes of K(trans) and ve during therapy and their different measurement levels within tumors and in normal appearing contralateral tissue.

MRI-based simulation of treatment plans for ion radiotherapy in the brain region.

PURPOSE: To test the potential of MRI-based treatment plan simulation for ion radiotherapy in the brain region. MATERIALS AND METHODS: A classification-based tissue segmentation method based on discriminant analysis was employed to derive so-called pseudo CT numbers from MR images of three patients with lesions in the head region undergoing ion radiotherapy. Treatment plans for ions, and for comparison purposes also for photons, were subsequently optimized and simulated using both MRI-based pseudo CT and a standard X-ray-based reference CT. RESULTS: Pseudo CTs revealed mean absolute errors in CT number in the range of 141-165 HU. While soft tissue was in good agreement with reference CT values, large deviations appeared at air cavities and bones as well as at interfaces of different tissue types. In simulations of ion treatment plans, pseudo CT optimizations showed small underdosages of target volumes with deviations in the PTV mean dose of 0.4-2.0% in comparison to reference CT optimizations. In contrast, the PTV mean dose in photon treatment plans differed by no more than 0.2%. CONCLUSIONS: The main challenge in deriving pseudo CT numbers from MRI was the correct assignment of air and compact bone. In this study, the impact of deviations on simulations of ion and photon treatment plans in the brain region was small, however for more complicated morphologies a further improvement of the classification method including MR imaging of compact bone is required.

7 Tesla imaging of cerebral radiation necrosis after arteriovenous malformations treatment using amide proton transfer (APT) imaging.

Arteriovenous malformations (AVM) can be treated with stereotactic radiosurgery. An infrequent, but important complication of this treatment is radionecrosis, which can be detected by MRI. However, the imaging characteristics of necrosis are unspecific in conventional MRI. Here, we report a case of necrosis after radiotherapy of an AVM to illustrate the potential of 7 Tesla MRI including amide proton transfer (APT) for necrosis imaging.

In vitro assessment of needle artifacts with an interactive three-dimensional MR fluoroscopy system.

PURPOSE: To perform in vitro assessment of needle artifacts with an interactive three-dimensional (3D) near-real-time magnetic resonance (MR) fluoroscopy system for musculoskeletal interventions in a 1.5-T open-bore magnet. MATERIALS AND METHODS: One MR-compatible titanium needle, one MR-compatible Inconel (nickel-chromium superalloy) needle, and one MR-compatible carbon fiber needle were imaged with an interactive 3D MR sequence. Slice orientations, measurement parameters (fast low-angle shot, repetition time/echo time of 1,358/5 msec, flip angle of 15 degrees , bandwidth of 250 Hz/pixel; and true fast imaging with steady-state precession, repetition time/echo time of 770/2.2 msec, flip angle of 50 degrees , bandwidth of 558 Hz/pixel), phase encoding directions, and orientations to the main magnetic field (B(0)) were systematically varied. Artifact sizes, normalized artifact contrasts, and tip location errors were assessed for all variations of acquisition parameters and needles and compared with t tests. RESULTS: Mean artifact sizes, normalized artifact contrast, and tip location errors were 22.9 mm, 96%, and 5.4 mm, respectively, for the Inconel needle; 6.1 mm, 70%, and 0.3 mm, respectively, for the titanium needle; and 2.8 mm, 38%, and -1.9 mm, respectively, for the carbon fiber needle. Artifact widths depended on needle materials and needle orientation to B(0), with significant differences on ttests. Artifact contrast did not depend on measurement parameters. No significant influence on artifact character was found for changes in phase encoding direction and slice orientation. CONCLUSIONS: Because of its robustness in depicting needle artifacts, the interactive 3D MR fluoroscopy system appears to be suitable for MR-guided interventions. The titanium needle showed optimal artifacts with all combinations of measurement parameters. Artifacts with the other needles were too large (Inconel) or too small (carbon fiber).